FIG. 14 shows a conventional LED module in a related art. As shown in FIG. 14, an LED module 900 has a structure where three LED chips 931, 932 and 933 are mounted on a long rectangular substrate 910. The substrate 910 is formed with a plurality of electrodes 921, 922, 923 and 924. The electrodes 921, 922 and 923 are respectively die-bonded with LED chips 931, 932 and 933. The electrode 924 is a so-called common electrode which makes electrical conduction with the LED chips 931, 932 and 933 via a wire. The three LED chips 931, 932 and 933 are surrounded by a case 950. The case 950 is made of frame-like opaque resin material and its inner space is filled with light transmitting resin (not shown). The LED module 900 is configured as a so-called side view type LED module which is mounted on a circuit board, with a lower surface (in the drawing) extending in a longitudinal direction of the substrate 910 as a mounting surface. The LED chips 931, 932 and 933 emit red, green and blue light, respectively. The LED module 900 is configured to emit white light by mixing the light from these LED chips 931, 932 and 933.
However, there are ever increasing requirements for reducing the size of the LED module 900. For example, in order to restrict a projecting height of the LED module 900 from the circuit board on which the LED module 900 is mounted, there is a need to make the substrate 910 more compact. This reduces the space for mounting the LED chips 931, 932 and 933. To mount the LED chips 931, 932 and 933, additional space, in addition to the space needed for the LED chips 931, 932 and 933, is needed for wires connected to these LED chips and a portion of the common electrode 924 to which these wires are connected. In addition, the area ratio of the electrodes 922 and 923 to the substrate 910 is not small. Thus, this makes it difficult to achieve a compact substrate 910.